There are known electrophotographic image forming apparatuses having an image carrying member which carries an electrostatic latent image, and a developing cartridge which supplies a developing agent to the electrostatic latent image on the image carrying member.
There is proposed, as a developing cartridge mounted to such an image forming apparatus, a developing cartridge including a frame, a developing roller supported at a rear end portion of the frame, and a layer thickness regulating blade supported at the rear end portion of the frame, for example.
This developing cartridge has a lower frame formed as a frame with a bottom but opened upwards and to the rear, and an upper frame which is assembled to the lower frame from above. The upper frame is welded to left and right side walls and a front wall of the lower frame, at left and right edge portions and a front portion of the upper frame.
A seal which seals between the rear end portion of the frame and the layer thickness regulation blade covers and seals the seam between left and right edges of the upper frame and the left and right side walls of the lower frame, from the rear side, that the left and right ends thereof.